Roentgenium ( IPA: /ˌrəʊntˈgɛniəm/) is a chemical element in the periodic table that has the symbol Rg and atomic number 111 making it one of the super-heavy atoms. It is a synthetic element whose longest-lived isotope has a mass of 280 and a half-life of 3.6 seconds. Due to its presence in Group 11 it is a transition metal and so probably would appear as a heavy, solid, shiny metal. Due to the inert pair effect, it should be colored like gold.

History

It was first created at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, Germany on December 8, 1994. Only three atoms of it were observed (all 272Rg), by the fusion of bismuth-209 and nickel-64 in a linear accelerator. (Nickel was bombarded onto the bismuth target.)

The name roentgenium was accepted as a permanent name on November 1, 2004 in honour of Wilhelm Röntgen; before this date, the element was known under the temporary IUPAC systematic element name unununium ( IPA: /ˌuːˌnuːˈnuːniəm/, symbol Uuu). Some research has referred to it as eka- gold.

The official baptism took place at GSI, on Friday November 17, 2006, in presence of Annette Schavan, the Federal German Minister of Research.

Isotopes

Three isotopes of roentgenium are known. The longest-lived of these is 280Rg which decays through alpha decay and has a half-life of 3.6 s. The shortest-lived isotope is 272Rg which decays through alpha decay and has a half life of 1.5 ms. The other known isotope, 279Rg, decays through alpha decay and has a half-life of 170 ms.

Trivia

The elements in Group 11 used to informally be called the coinage metals, due to their historical use in coins. It is unlikely that roentgenium can be used to make coins since all of its isotopes are radioactive with very short half-lives.

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